Flame arrestors are used in pneumatic control devices to provide a flameproof path for the pneumatics into and out of a control or instrument. Flame arrestors provide a restricted pneumatic passage over an extended length such that a flame cannot propagate through the passage.
Several types of arrestors are known in the art. A sintered metal arrestor has been commonly used; however, recently adopted European standards no longer permit the use of this type of flame arrestor. Another type is a Lisk arrestor which is comprised of layers of crimped and flat sheet metal that are wrapped together and held in a case by a rivet. Other types include the parallel plate types that usually consist of flat plates with a slot ground into the plate to a depth equal to the maximum gap allowed for the length of the flame path. The plates are then stacked and bonded together at the unground area to form a series of parallel flame retardant paths. This type of construction is quite expensive due to the grinding of the slot, and the arrestors are more bulky due to the solid area that supports the gap and forms the bond area. Another type of flame arrestor would be a gear shaped rod that is pressed into a tube with the flameproof path provided between the gear teeth. This type of arrestor would be quite expensive as it requires the machining of the fine gear teeth, and it would provide a restricted flow area. These types of flame arrestors are expensive to make and require fine machining of the various parts.
Since the allowable gap dimensions in small flame arrestors are very small, manufacture of a small flame arrestor is particularly difficult and expensive. Thus, a need exists for an easy, economical method of manufacturing precision flame arrestors, both small and large, that would meet the necessary standards here and abroad.